Parasitic loop counterpoise antenna

ABSTRACT

An antenna system comprising an active radiating element, such as an Alford loop, for radiating electromagnetic energy, a surface positioned below the radiator element to form a ground plane or counterpoise, and one or more passive parasitic loop elements positioned above the radiator so that the radiation from the parasitic elements is of a magnitude and polarity to cancel the radiation field below the plane of the counterpoise.

United States Patent Inventors Appl. No.

Filed Patented Assignee PARASITIC LOOP COUNTERPOISE ANTENNA [50] Fieldof Search 343/834, 845. 846. 847. 848, 899, 908. 741, 837

[56] References Cited UNITED STATES PATENTS 2,998,605 8/ l 961 Orlando343/848 Primary Examiner-Eli Lieberman Attorneys-Alva H. Bandy, WilliamG. Gapcynski and Lawrence A. Neureither ABSTRACT: An antenna systemcomprising an active radiating element, such as an Alford loop, forradiating electromagnetic energy, a surface positioned below theradiator element to form a ground plane or counterpoise, and one or morepassive parasitic loop elements positioned above the radiator so thatthe radiation from the parasitic elements is of a magnitude and polarityto cancel the radiation field below the plane of the counterpoise.

3 Claims, 5 Drawing Figs.

US. Cl 343/837, 343/741, 343/848 lnt.Cl ..H0lq 19/10 PATENTEU SEP14l97l3,505,104

MEASURED FAR FIELD ELEVATI PATTERNS OF VOR A NTENN 3 64in): Q4" m @4630lNVE/V VAUGHAN H. WEST DIPAK L. SENGUPTA JOSEPH E. FERRIS FIG.5

ATTORNEY PARASITIC LOOP COUNTERPOISE ANTENNA BACKGROUND OF THEINVENTION 1. Field of the Invention Th.s invention relates to animproved counterpoise antenna in which the radiation field below theplane of the counterpoise has been substantially reduced by the additionof parasitic loop elements above the radiator element.

2. Description of the Prior Art Often va particular application requiresan antenna system which produces radiation above a given plane but doesnot establish a radiation field below the plane. Counterpoise antennasare normally used for this purpose, but due to the finite size of thecounterpoise surface, edge diffraction effects cause a certain amount ofradiation to be directed below the plane of the counterpoise, thusproducing undesirable effects. For example, a counterpoise antennaideally suited for use in an existing VHF Omni Range (VOR) system wouldproduce no radiation field below the plane of its counterpoise. Existingantennas, however, due to the counterpoise edge diffraction effects,have considerable response in directions below the plane of thecounterpoise. Because of the existence of a radiation field below theplane of the counterpoise, ground reflection effects and scattering fromobjects such as trees and buildings in the vicinity of VOR installationsproduce errors in the VOR bearing indicators. Elimination of theseeffects using present antenna systems would require an infinitely largecounterpoise, and extension of counterpoise diameters beyond thosepresently used is impractical. One proposed solution involved the use ofa stacked array of a plurality of Alford loop antennas above acounterpoise. By properly choosing the amplitude and phase of theexcitation of the loops, the rate of decrease of the electromagneticfield below the horizon can be increased. Successful operation of thissystem requires proper phasing and feed networks for the Alford loops,and although the theoretical value for the rate of decrease of field ishigh, the actual response of the antenna below the plane of thecounterpoise was found to be quite high. Horn and lens antenna systemstheoretically provide partial solutions; however, the extreme size ofthese systems at the frequencies presently employed makes their useimpractical.

SUMMARY OF THE INVENTION This invention substantially reduces theradiation field existing below the plane of the counterpoise of acounterpoise antenna system by using one or more parasitic loop elementspositioned above the active radiator element. The parasitic loop orloops are positioned so that the radiation resulting from the electriccurrent induced in the parasitic element by the electromagnetic fieldproduced by the active radiator element is of proper magnitude and phaseto cancel the radiation field existing below the plane of thecounterpoise.

It is therefore an object of the invention to provide a counterpoiseantenna system which has a minimal radiation field below the plane ofthe counterpoise.

It is a further object of the invention to provide an improvedcounterpoise antenna system which can be used with existing VOR systems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a particularembodiment of the invention.

FIG. 2 is a cross-sectional view taken along the line 22 of FIG. 1.

FIG. 3 is a graph showing the radiation field pattern of both aconventional counterpoise antenna and a counterpoise antenna with theinvention.

FIG. 4 is a cross-sectional view of an alternative embodiment of theinvention showing a collinear arrangement of the parasitic elements.

FIG. 5 is a cross-sectional view of an alternative embodiment of theinvention showing a coplanar arrangement of the parasitic elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2there is shown an antenna system comprising an active radiator element2, such as an Alford loop, for radiating electromagnetic energy, asurface 1 positioned below the radiator element to form a counterpoiseor ground plane, and one or more parasitic loop elements 3 positionedabove the radiator element. The active radiator element 2 is chosen tofit the needs of the particular situation, and application of theinvention is not restricted to a particular type of class of radiatorelements. The radiator element 2 is structurally supported above thecounterpoise in a conventional manner so that the radiator element iselectrically insulated from the counterpoise 1. FIG. 2 illustrates onepossible manner of supporting the radiator element 2 through use of aninsulating material 4 surrounding a transmission line 5 to supply theradiator element 2 with energy.

The counterpoise l is composed of a metallic substance so that aconductive plane surface is formed, and its dimensions are preferablylarge compared to the wave length of the radiator element.

The system also comprises one or more passive loop elements 3 positionedabove the radiator element 2. The parasitic element or elements may bestructurally supported above the counterpoise 1 by means of dielectricsupport members which for the sake of simplicity have not been shown.These passive elements are made of a conducting metallic substance andare formed into a closed loop which may be of any desired crosssectionalconfiguration. One or more of the parasitic loop elements 3 may be used,and they may be successively stacked above the radiator element 9 asshown in FIG. 4 and referred to as a collinear system so that all theparasitic elements 8 share a common longitudinal axis with the radiatorelement 9. Alternatively as shown in FIG. 5, the parasitic loop elements10 may be concentric about a central parasitic element 11 positionedabove the radiator element 12 and referred to as a coplanar system sothat all the parasitic loop elements share a common longitudinal axiswith the radiator element. The dimensions of the parasitic loopelements, their relative positions, and the number of parasitic elementsemployed are determined by mathematical calculations well known to thoseskilled in the art based on the desired radiation field distribution.

The radiation produced by the parasitic elements is calculated throughthe use of conventional techniques of electromagnetic field analysis bydetermining the current induced in the parasitic elements by theradiation field from the active radiator element. This parasiticradiation is then summed with the radiation from the active element todetermine to total radiation field propagated by the system. As thiscalculation may be made in terms of the dimensions and placement of theparasitic elements, the parameters of the parasitic elements may becompletely specified for a desired radiation field.

An embodiment of an antenna system constructed in accordance with theinvention described herein is illustrated in FIGS. 1 and 2. Therequirements of this system were that the radiation field beomnidirectional above the plane of the counterpoise, and that it be zerobelow the plane of the counterpoise. An Alford loop antenna, describedin US. Pat. No. 2,283,897, was selected as the active radiator elementbecause of its omnidirectional radiation field characteristics, and itwas positioned 0.44)\ above the counterpoise. One parasitic loop elementwith a diameter of 2.5% was used, and it was positioned 0.59% above thecounterpoise. The loop was formed from a brass strip of rectangularcross section with a thickness of 9.l5 10 and a width of l.83 lO Thecircular counterpoise was cut from an aluminum sheet of 0.125- inchthickness, and it had a diameter of 5.7).. A frequency of 1080 MHz, wasused to excite the active radiator element.

The radiation field produced by the improved antenna system is shown bythe solid line 6 in FIG. 3. The broken line 7 represents the radiationfield obtained from the Alford loop and the counterpoise without theparasitic loop element. It can be seen from FIG. 3 that the improvedantenna system has practically eliminated the radiation field below theplane of the counterpoise.

We claim:

I. An antenna system comprising a counterpoise in the form of aconducting metal surface, a radiator element for radiatingelectromagnetic radiation positioned above said counterpoise, andparasitic means comprising a plurality of circular loop elementspositioned above said radiator element so that said radiator element isintermediate said parasitic means and said counterpoise and positionedin cooperative relation thereto as a function of the frequency ofradiated energy.

2. The device of claim 1 in which said circular loop elements aresuccessively stacked above said radiator element so that said circularelements share a common longitudinal axis with said radiator element.

3. The device of claim I in which said circular loop elements areconcentric about a central circular element positioned above theradiator element to that said circular elements are located in the sameplane and share a common longitudinal axis with said radiator element,the mutual spacing of said circular elements and the spacing of saidelements relative to said counterpoise and said radiating elementrelative to said counterpoise being a function of the frequency ofradiated energy.

1. An antenna system comprising a counterpoise in the form of aconducting metal surface, a radiator element for radiatingelectromagnetic radiation positioned above said counterpoise, andparasitic means comprising a plurality of circular loop elementspositioned above said radiator element so that said radiator element isintermediate said parasitic means and said counterpoise and positionedin cooperative relation thereto as a function of the frequency ofradiated energy.
 2. The device of claim 1 in which said circular loopelements are successively stacked above said radiator element so thatsaid circular elements share a common longitudinal axis with saidradiator element.
 2. Although the characteristic curve is mild ingradient than that of the solid electrolyte obtained in Example 1, thissolid electrolyte is superior to the conventional one as may be readilyappreciated upon comparison with the curve 1 representing thecharacteristic of the latter. Examples 3 to 8 Solid electrolytes wereproduced in the same manner as in example 1 but by mixing CeO2, Gd2O3and MgO in the proportions shown in table 2 below. These solidelectrolytes had pecific resistance--temperature characteristics asshown in FIG. 3 respectively.
 2. A fuel cell of oxygen-hydrogen type asdefined in claim 1, in which x and y representing mol numbers of 2O3 andMgO respectively arssssssssss
 3. The device of claim 1 in which saidcircular loop elements are concentric about a central circular elementpositioned above the radiator element to that said circular elements arelocated in the same plane and share a common longitudinal axis with saidradiator element, the mutual spacing of said circular elements and thespacing of said elements relative to said counterpoise and saidradiating element relative to said counterpoise being a function of thefrequency of radiated energy. FIG. 10 is a sectional view of an oxygenrefiner in which the solid electrolyte according to the presentinvention is used; and FIG. 11 is a characteristic curve of the oxygenrefiner, showing the relationship between the effluent rate of produceoxygen and the voltage. DESCRIPTION OF THE PREFERRED EMBODIMENTSReferring first to FIG. 1, the characteristic curves show therelationship between the composition of the electrolyte of thisinvention, consisting essentially of 2 mols of CeO2, x mol of Gd2O3 andy mol of MgO, and the specific resistance of the electrolyte at specifictemperatures. The curve 1 is curve on which the electrolyte shows aspecific resistance of 80 Omega cm. at 725* C., and the region inside ofthe curve is a region in which the electrolyte shows a specificresistance smaller than 80 Omega cm. and the region outside of the curveis a region in which the electrolyte shows a specific resistance largerthan 80 Omega cm. The curve 2 is a curve on which the electrolyte showsa specific resistance of 30 Omega cm. at 800* C. and the region insideof this curve is a region in which the electrolyte shows a specificresistance smaller than 30 Omega cm. Namely, this curve epresents anelectrolyte which is superior to thaT represented by the curve